Leaves: Stem leaves flat against the stem (or frequently spreading on sympodial shoots), densely overlapping, widely egg-shaped, cupped, somewhat to not at all longitudinally pleated, cupped, 1.5-2.5 mm in length, 0.8-1.5 mm in width; margins flat or curved back and downward in different locations; base curved, with long, wide decurrencies; apex slowly narrowing, the tip widely acute (seldom acuminate); costa distinct, extending about 1/2-3/4 the length of the leaf. Branch leaves narrower (lance-shaped and somewhat ovate) and spreading more than the stem leaves, the length 2-3 times that of the width (FNA 2014), not or only shortly decurrent (Crum and Anderson et al. 1981).

Stem Leaf Cells: Alar cells highly inflated and fine-walled, short and quadrangular (FNA 2014), forming auricles which extend down the stem (Lawton 1971), the alar area large and well-delineated, from near the edge extending about half the distance to the costa; laminal cells long and thin; basal cells arranged in 3 tiers (FNA 2014).

Plants influenced by swift currents are rigid and brownish-green rather than soft and pale, whitish green like those plants found near springs (FNA 2014).

Both robust forest species, Brachythecium rivulare has a somewhat tree-like appearance, and the sympodial shoots with their branches are not as crowded as in the similar B. rutabulum. Although both species have inflated alar cells, the alar area of B. rivulare also includes cells that are slender and chlorophyllous near the margin, which B. rutabulum does not (FNA 2014).

Species Range

Present

Range Comments

North American Range

Found in most states and provinces (unknown in CA, ND, TX, and a few southeastern states) (FNA 2014). In Montana, known from Beaverhead, Carbon, Cascade, Fergus, Flathead, Gallatin, Glacier, Lake, Lewis and Clark, Lincoln, Madison, Missoula, Park, Powell, and Ravalli Counties (Elliott 2016).

Lawton, E. 1971. Keys for the Identification of the Mosses on the Pacific Northwest. Reprinted from 'Moss Flora of the Pacific Northwest'. Published as Supplement No. 2 of the Journal of the Hattori Botanical Laboratory. Nichinan, Miyazaki, Japan. 66 pp.